Hello
When I was young I dreamed that I would have curly hair like my siblings who had dark ringlets while I had pin straight fine blonde hair. And presto one day as my hair was drying a single baby curl appear at my neck, I took this as a fluke, but as the months went by sections of my hair would curl. I was excited, but my the curls were quiet frizzy so I would brush them and the would virtually disappear. Fast forward a few years and my hair is curly everywhere except the very top of my hair in the front and becoming coarse in the back (not very attractive). Here is the problem though, my curls are frizzy and almost every strand is damaged even though I very rarely used a blow dryer or straighter. My question to you guys is a) why did my hair change from fine nearly white straight hair to coarse curly damaged frizzy dirty blonde hair and b) any recommended products would help my prone to splitting and frizzy hair?

(I would say my hair is 3a maybe, some strands make loose s's other circles depending on the day)